Bolt element having a shaft part and a spherical head, component assembly and method for the manufacture of a bolt element

ABSTRACT

Bolt element ( 10 ) having a shaft part ( 12 ) which is designed at a first end ( 14 ) for a rivet connection ( 16 ) to a panel element ( 18 ), in particular to a sheet metal part, is characterized in that the shaft part ( 12 ) has a spherical formation ( 22 ) at its other end ( 20 ) the ball diameter (D) of which is larger than that of the shaft part ( 12 ). In this manner a bolt element with a spherical head can be manufactured in an extremely favorable manner price-wise and it can be ensured that the spherical head has no burr which would lead to the wearing of the socket provided in operation which slides on the spherical head.

The present invention relates to a bolt element having a shaft partwhich is designed at a first end for a rivet connection to a panelelement, in particular to a sheet metal part. Furthermore, it relates toa component assembly comprising a bolt element of this kind with acomponent as well as to a method for the manufacture of such a boltelement:

A bolt element of the initially named kind is known from theInternational Application PCT/EP00/06465 or from the correspondingGerman Patent Application 100 33 149.1 as well as from the InternationalApplication PCT/EP00/06468 and from the corresponding German PatentApplication 100 22 152.1.

One problem in mechanical engineering is to manufacture favourablypriced bolt elements with a spherical head. Such bolt elements are forexample used as hinge elements for damped spring supports which are usedto support boot lids or bonnets (hoods) of motor cars. Such hingeelements are however also found in a plurality of other constructions,for example in linkages in the actuation mechanism of carburetors andthe like.

The known spherical bolt elements have a thread at the shaft part and aflange projecting radially from the thread so that the bolt element canbe fixedly installed on a sheet metal part or carrier. This design ofthe shaft part of the bolt element also makes it difficult tomanufacture the spherical head because it gives riser to restrictions inthe design of the cold heading tools for the spherical head.

In the known bolt elements for the spherical head it is problematic thatwhen these are to be manufactured at favourable cost as cold headedparts the movable tool parts which form the spherical head have to moveradially towards the longitudinal axis of the bolt elements and thatburrs form at the surface of the spherical head at the partitionsurfaces, i.e. where these tool parts meet one another, with the burrseach lying in a radial plane. These burrs, even if they are fine innature must either be removed in a costly manner in a further process orone was must accept the disadvantage that the burrs relatively quicklylead to wear of the socket which receives the spherical head,irrespective of whether the socket consists of plastic or metal.

The object of the present invention is to provide a bolt element with aspherical head which can be manufactured at extremely favourable costand nevertheless does not have any disturbing burr. Moreover, afavourably priced attachment of a bolt element to a component should bemade possible, so that the corresponding component assembly can likewisebe obtained at a favourable price. Furthermore, a favourably pricedmethod for the manufacture of a corresponding bolt element is to beprovided.

In order to satisfy this object a bolt element of the initially namedkind is provided with the special characterizing feature that the shaftpart has at its other end a spherical formation, the ball diameter ofwhich is larger than that of the shaft part.

In other words the bolt element in accordance with the inventionconsists essentially of a spherical head and a cylindrical shaft part,which is hollow at its end remote from the spherical head in order toenter into a rivet connection with a panel element, in particular with asheet metal part. Since the diameter of the shaft part is constant, thefunctional element can be manufactured in that a cylindrical blank isreceived in accordance with claim 14 partly in a cylindrical passage ofa die and projects beyond the end face of the die, in that ahemispherical recess is formed in the die in the region of thetransition of the passage into the end face with the ball diameter ofthe hemispherical recess corresponding to the ball diameter of thedesired spherical formation of the bolt element, in that a tool with alikewise hemispherical recess is pressed onto the free end of thecylindrical blank projecting out of the die and the die and the tool arebrought into contact with one another in order to reshape the end of thecylindrical blank projecting out of the die to the spherical formationby cold deformation.

Whereas, in the prior art, the cold heading tools which are used for themanufacture of the spherical head have to be moved in the radialdirection relative to the longitudinal axis of the corresponding blankin the invention the tools, of which there are only two, namely the dieand the tool which cooperates with it, are, so to say, arrangedcoaxially to the cylindrical blank and are moved towards one another inorder to produce the spherical formation by cold deformation of thecylindrical blank. This signifies that in the closed state of the dieand of the tool, i.e. when these contact one another at a partitionsurface this partition surface is located at a position whichcorresponds to an equator of the spherical formation and standsperpendicular to the longitudinal axis of the cylindrical blank or ofthe shaft part of the bolt element.

In this design it is on the one hand possible to guide the die and thetool in such a way that they are strictly aligned relative to oneanother and that only an extremely small burr is formed in the region ofthe equator, if at all. This burr is however also no longer sodisturbing because it does not exert any pronounced scraping action onthe socket on rotating the socket about the longitudinal axis of thespherical head, as is the case of a burr which extends in a radialplane. Because the shaft part of the functional element is made at leastsubstantially cylindrical and has a constant outer diameter, thecylindrical blank can be made at extremely favourable cost fromcylindrical bar material or wire or can be manufactured from tubematerial. A radial movement of the parts of the die or of the tools inorder to take account of the features of shape of the shaft parts is nolonger necessary, since no such features of shape are present in apurely cylindrical shaft part.

Through the design of the rivet connection in accordance with the mannerdescribed in the above-named PCT applications, or in the correspondingGerman patent applications, it is nevertheless possible to secure thecorresponding bolt element at favourable cost and with adequate strengthto a component or to a sheet metal part.

In the first case (in the case of PCT/EP00/06465) the bolt element has aform designed there as a head part in the shape of a hollow cylinderwhich is equipped with piercing arid riveting features and which isintroduced in a self-piercing manner into a sheet metal part. In thisarrangement the free end of the hollow head part is formed over to arivet bead at one side of the sheet metal part and the wall of thecylindrical part is formed into a ring fold at the other side of thesheet metal part, so that the sheet metal part is clamped between therivet bead and the ring fold. In this way a stable connection arisesbetween the bolt element and the sheet metal part. In the second case(in the case of the PCT Application PCT/EP00/06468) the bolt elementlikewise has a section termed there as the head section which is againformed as a hollow cylinder but which is strongly rounded at its openend face and thus has in total a cigar-like shape.

In both cases the respective element has an at least substantiallyconstant diameter over its entire length in preferred embodiments.

In the case of the cigar-like element this is not introduced inself-piercing manner into the sheet metal part, but rather the hollowregion of the bolt element is exploited to press the sheet metal partinto a shaping space of a die and is deformed during this into two axialring folds spaced from one another by a ring recess with the sheetmaterial being pressed into the ring recess and thus producing a stablerivet connection between the bolt element and the sheet metal part. Theshaft parts of the respective bolt elements are normally provided withan outer thread. Other formations, such as a peripherally extendinggroove to receive a spring clamp are also described. The disclosures ofthe above designated international applications or of the correspondingGerman applications are also made part of the content of the presentapplication since the designs respectively de scribed there, for therivet connections to the sheet metal part, can be used in identical formin the present invention and represent preferred embodiments of therivet connection which will be used for the present invention.

In both cases the deformation of the hollow region of the shaft part atits first end remote from the spherical head leads to an adequatelybroad ring fold which enables a good attachment to the sheet metal partand so to say forms a broad base so that forces which act in the radialdirection on the spherical head do not lead to a loosening of the boltelement.

Particularly preferred embodiments of the bolt element and also of thecomponent assembly, of the method and also of the die and tools inaccordance with the present invention can be taken from the descriptionof the Figures and also from the subordinate claims. The invention willnow be explained in more detail with reference to embodiments and to thedrawing in which are shown:

FIG. 1 a bolt element in accordance with the invention sectioned partlyin the longitudinal direction,

FIG. 2 the tools used in accordance with the invention for themanufacture of the bolt element of the invention of FIG. 1,

FIG. 3 a diagram corresponding to FIG. 5 of the PCT ApplicationPCT/EP00/06465 in order to explain the attachment of the bolt element ofthe invention to a sheet metal part,

FIG. 4 a Figure corresponding to FIG. 2 of the PCT ApplicationPCT/EP00/06468 in order to show the use of the rivet connection of thisPCT Application in the present invention,

FIG. 5 a representation sectioned in the longitudinal direction of aspherical bolt element, which was manufactured from tube material,

FIG. 6 a similar illustration to that of FIG. 6 of a spherical boltelement which was manufactured by means of an internal high pressureforming process,

FIG. 7 a preferred tool for the attachment of spherical bolt elements,

FIG. 8 a detail of the die of FIG. 7 in the region of the rectangledrawn in there without sheet metal part,

FIG. 9 the detail of FIG. 8 after the attachment of the spherical boltelement and

FIGS. 10A to 10D a series of sketches to illustrate different possiblesheet metal preparation steps.

In the following description the same reference numerals will always beused for the same or similar parts and features, so that a descriptionwhich has been given once of a part or of a feature also applies to apart or feature with the same number and the description need not berepeated.

FIG. 1 shows in a side-view a bolt element 10 in accordance with theinvention and having a shaft part 12 which is designed at a first end 14for a rivet connection 16 (see FIG. 3) to a panel element 18 togetherwith a sheet metal part. The shaft part 12 has at its other end 20 aspherical, formation 22, the ball diameter D of which is larger than thediameter d of the shaft part.

The diameter d of the shaft part 12 is at least substantially constantover at least substantially its whole length from the sphericalformation 22 up to the end face 24 of the first end 14.

The first end 14 of the shaft part 12 which is designed for the rivetconnection 16 to the sheet metal part is made hollow and has at leastsubstantially the same outer diameter d as the remainder of the shaftpart 12: The hollow space 26 which is formed in this way is, as shown inFIG. 1, at least substantially of circularly cylindrical shape. Thefirst end 14 of the shaft part 12 is formed in a manner known per sewith piercing and riveting features, and indeed in the form of a roundedpunching and drawing edge 28 and has a conical cutting surface 30 at itsinside. The piercing and riveting section of the bolt element 10 is thusformed in accordance with DE-PS 34 470 06 C2. The outer periphery of theshaft part 12 is preferably also made circularly cylindrical, i.e. ithas in cross-section a circular periphery. It would however also beconceivable to use shapes of the shaft part 12 which differ slightlyfrom the circular shape, for example a polygonal shape should thisappear expedient for special reasons.

The hollow region 32 should have a minimum length L (measured in thedirection of the central longitudinal axis 34 of the bolt element 10) toensure that adequate material is present in the hollow region in order,during the formation of the rivet connection 16 of FIG. 3, to form therivet bead 36 at the side 38 of the component 18 remote from thespherical formation 22, to bridge the thickness of the component 18 andto form the ring fold 40 at the side 42 of the component 18 adjacent thespherical formation.

It is also conceivable to make the bolt element hollow as a whole whichwould have the advantage that the element could be manufactured fromtube material and that the spherical formation could be manufactured bya high pressure shaping process inside a corresponding outer die.

When using a hollow shaft part this can optionally be provided with aninternal thread whereby, after formation of the rivet connection of FIG.3 and removal of the stamping slug 44 shown there, a bolt could beintroduced into the thread from the end of the bolt element 10 remotefrom the spherical formation 22 in order to additionally enhance theattachment to the sheet metal part, should this be necessary. A boltelement of this kind could also increase the stiffness of the boltelement itself. With such a design (not shown) it will be necessary toprovide correspondingly shaped washers for a stable seating of the headof the bolt at the underside of the sheet metal part 18 for which itwould be sufficient, under such circumstances, to provide the rivet bead36 with a flattened lower side (in FIG. 3) by a pressing process.

It is moreover evident from FIG. 1 that the spherical formation 22 hasan equator line 46 which lies in a plane which stands perpendicular tothe longitudinal axis 34 of the shaft part. At the position of theequator line 46 there is essentially no burr, i.e. no raised portion tobe found during the manufacture of the bolt element, but rather thisequator 46 merely shows the position of the parting joint of the toolswhich are used to form the spherical formation. These tools are shown inmore detail in FIG. 2. They comprise a lower die 50 and an upper tool52. The designation ‘lower and “upper” relates here, as also at otherpoints of the description and claims solely to the alignment of thedrawing and does not represent any restrictions on the actual alignmentof the die or of the tool. These parts could just as easily be arrangedso that the die is disposed above the tool 52 or such that the centrallongitudinal axis 54 is arranged horizontally or in another direction.

The die 50 has a cylindrical passage 56 which merges, in the region ofthe end face 58 of the die, into a hemispherical recess 60 the sphericaldiameter of which corresponds to the diameter D of the sphericalformation 22 of the bolt element 10. Within the central passage 56 ofthe die there is located a cylindrical bar 55, the upper end 64 of whichis located in the hollow space 26 of the bolt element 10 and, forexample, contacts the transverse wall 66 of the hollow space 26. At itsother, lower, end the bar 62 is supported on a firm support, as is thedie 50. The bar 62 is located within a sleeve 68 which can be moved toand fro in accordance with the double arrow 70 in order to eject thefinished bolt element 10 out of the die.

Above the die 50, and coaxially aligned with it, is a tool 52 whichlikewise has a hemispherical recess 74 at its end 70, with thishemispherical recess 74 also merging into a circularly cylindricalpassage 76 which is likewise arranged coaxial to the centrallongitudinal axis 54. The reference numeral 80 points in this embodimentto a cylindrical guide which is located in the passage 76 and the lowerend 82 of which serves to produce the flat 84 at the upper end of thespherical formation 22. This guide 80 can also be biased with a springdevice so that it can deflect by a small amount if, for tolerancereasons, too much material is present for the generation of thespherical formation 22.

The manner of operation of the arrangement in accordance with FIG. 2will now be explained in more detail. Initially all the bolt element 10should be imagined to be missing. First of all a cylindrical blank (notshown) which has the hollow space 26 and the piercing and rivetingfeatures is introduced into the central passage 56 of the die 50 so thatthe transverse wall 66 is supported on the upper side of the bar 54. Theejection sleeve 68 is retracted in this state so that the lower end face24 of the blank has a distance from the sleeve 68 or can press this awaywith a light contact pressure. The upper die 52 is now guided downwardlyunder the guidance of the guide bar 80 and deforms the upper end of thecylindrical blank into the spherical form 22. At the end of the movementof the tool 52 towards the die 50 the lower end face 72 of the tool 52is in contact with the upper end face 58 of the die SO and the partitionjoint, i.e. the position at which the end faces 72 and 58 contact oneanother, is so selected that it lies on the equator line 46 of thespherical formation. The cylindrical blank is so dimensioned that itprojects prior to the closing movement of the tool 52 against the die 50beyond the end face 58 of the die 50 and indeed by an amount such thatjust sufficient material is present in order, in the closed state of thetools, i.e. with contact of the end face 72 of the tool 52 against theend face 58 of the die 50 to fill out fully the so formed sphericalspace.

As soon as the tools have reached this closed position the bolt elementis finished, the tool 52 is moved upwardly again and away from the die50 and the sleeve 68 is moved upwardly in order to eject the finishedbolt element 10, as shown in FIG. 2, out of the die 50. Thereafter a newcylindrical blank can be inserted into the passage 56 and the method isrepeated in order to manufacture a further bolt element.

The die 50 can be arranged in this manufacturing process and the lowertool of a press, whereas the upper tool 52 is attached to the upper toolof the press or to an intermediate platen of the press.

The method for attachment of the bolt element 10 to a sheet metal part18 as shown in FIG. 3 is described in detail in the above-mentioned PCTApplication PCT/EP00/06465 and will not be explained here in furtherdetail because the precise nature and design of the rivet connection isnot the subject of the present invention. Since the lower end of thebolt element 10 is equipped with piercing and riveting features it canbe introduced in self-piercing manner into the sheet metal part 18,whereby the punching slug 44 arises. As shown in FIG. 3 this punchingslug is clamped into the deformed hollow space 26 of the bolt element 10and contributes to the stability of the rivet connection 16. The upperside 90 of the ring fold 40 is so arranged that it lies approximately inthe same plane as the upper side 42 of the sheet metal part 18 and itdoes not therefore present any obstacle for the freedom of movement of asocket placed onto the spherical formation 22. One can see from theshape of the (originally flat) sheet metal part in the region of therivet connection 16 how an extremely stable attachment of the boltelement 10 to the sheet metal part 18 is provided.

The bolt element 10 need not essentially be executed as shown in FIG. 1but rather other designs of the first end 14 are conceivable which arealso suitable for a rivet connection to a sheet metal part. Inparticular a design can be considered as shown in FIG. 2 of the PCIApplication PCT/EP00/06468. This design also enables a rivet connection16′ as shown in FIG. 4 and is likewise realized as set forth in thementioned PCI Application. Advantageous for this type of rivetconnection is the fact that the sheet metal part 18 is not pierced, sothat a water-tight connection is present. As can be read in thecorresponding PCI Application the rivet connection 16′ is effected herein such a way that the hollow region of the bolt element is formed intotwo ring folds and indeed an upper ring fold 40′ and additionally alower ring fold 92 which form a ring-like recess 94 between them. Thesheet metal material is pressed into this ring-like recess 94 by theattachment of the sheet metal element, as shown at 96 in FIG. 4, and isfirmly clamped between the two ring folds 40′ and 92. The referencenumeral 98 points in this example to noses providing security againstrotation which are important in the PCI Application if the correspondingelement has to take up torques about the longitudinal axis.

Since one is concerned here with a bolt element with a spherical head,which does not have to take up any torques, such noses 98 providingsecurity against rotation are not compulsory and the correspondingfeatures of shape of the tools which are necessary to form theses nosespro viding security against rotation can be omitted.

In all embodiments all materials can be named as an example for thematerial of the functional elements which achieve the strength values ofclass 8 in the accordance with the ISO standard in the context of coldforming, for example a 35B2 alloy in accordance with DIN 1654. The soformed fastening elements are suitable, amongst other things, for allcommercially available steel materials for example drawing quality sheetmetal parts and also for aluminum or other alloys.

FIG. 5 shows an axial cross-section through a spherical bolt element 10similar to the spherical bolt element 10 of FIG. 1 but with thedifference that the element was manufactured from tube material and thushas a through-going central passage 100 with a circular cross-section.The lower end of the element of FIG. 5 can be formed in correspondencewith the lower end of the bolt element of FIG. 1 with piercing andriveting features in the form of a rounded pressing and drawing edge 28and a conical cutting surface 30, is however shown here in an embodimentin which the conical cutting surface 30 was reduced to a minimum, whichis also possible. The lower end of the longitudinal passage 100corresponds to the hollow space 26 of the spherical bolt element 10 ofFIG. 1 or forms this hollow space.

The spherical bolt element 10 is manufactured in accordance with thespherical bolt element 10 of FIG. 1 in a tool corresponding to FIG. 2but with the difference, that the guide bar 80 is preferably providedwith a cylindrical projection (not shown) which fits into the centrallongitudinal passage 100 of the tubular blank or of the spherical boltelement and extends downwardly approximately to the upper end of theguide bar 62 in order to support the tube material from the insideduring the formation of the spherical head and to avoid undesireddeformations of the tube material. The step between the bar 80 and thedownwardly directed cylindrical process, which also serves as a guidespigot and is introduced into the central longitudinal passage of theelement forms a radial shoulder which takes care of the flattening 84 atthe upper end of the spherical head.

FIG. 6 shows an alternative design of a spherical bolt element 10 whichis manufactured of tube material. In this case a circularly cylindricaltube section is laid into a two-part die (not shown) which has the outershape of the finished spherical bolt element of FIG. 6 as a hollowcavity. The lower end 24 in FIG. 6 of the spherical bolt element 10 issupported against a transverse wall of a hollow cavity of the mould andhydraulic fluid is forced at high pressure into the interior of the tubesection via the upper end of the tube section in FIG. 6 by means of asuitable nozzle, so that the spherical shape of the spherical head isproduced by the high pressure applied to the inner side. The two-partmould, which is not shown, but which is formed in the region of thespherical bolt elements in accordance with the tool 52 and the die 50has a partition surface between the two halves of the mould at thelevel, of the plane 102 which is shown in FIG. 6. After formation of thespherical bolt element 10 the mould is opened and the spherical boltelement can be moved from the mould, optionally with the aid of a sliderwhich slides in the axial direction of the shaft part of the sphericalbolt within one of the form halves and preferably presses against thelower end face 24 of the spherical bolt element 10 in FIG. 6.

FIG. 7 shows a preferred tool 104 for the attachment of a spherical boltelement, for example in accordance with FIG. 1, to a plate-likework-piece in the form of a sheet metal part 18. The sheet metal part 18is supported on the upper end face of a die 104 which, in its basicprinciples resembles the dies of the European Patent Application 99 120559.2 and of the European Patent Application 00 931 155.6. In accordancewith FIG. 9 of the first named patent application the die 104 which ispresent here has a hollow body 106 with an end face 108 provided for thesupport of a sheet metal part merging via a conically tapering wall 110into a space having an abutment element 112, with the abutment element112 being spaced from the conically tapering wall for the formation of aring gap 113 which is wedge-like in cross-section.

In the wedge-like ring gap there are a plurality of segment-like shapedparts of the same design, for example from 1 to 8, in particular 4shaped parts 116 which are arranged around the longitudinal axis 118 ofthe die in the wedge-like ring gap 113 and are supported both at theconical wall 110 and also at the abutment element 112. The shaped parts116 can either be so arranged that they completely fill out the ring gap113 around the longitudinal axis 118, i.e. so that no structure ispresent between neighbouring shaped parts 116, for example in accordancewith FIG. 10 of the EP Application 99 120 559.2, or fixed structure ofthe die can be provided between the adjacent shaped parts of the die, asin the die of EP Application 00 931155.6 or of the earlier related dieof the same inventor.

The abutment element is however designed in this embodiment somewhatdifferently than in the named EP applications.

First of all it is evident that the abutment element 112 has aring-like, radially extending, collar 120 which engages intocorresponding grooves 122 of the shaped parts, with the abutment element112 being movable with the shaped parts in the axial direction 118 ofthe die 104. The lower end 124 of the abutment element projects into ahollow space 126 of the die body 106 and is terminated there with a diskelement 130 screwed on by means of a screw 128. In this hollow space 126there is a compression coil spring between the radially inwardlyprojecting shoulder 132 of the outer part of the die and the die 130,with the compression coil spring being designed to draw the abutmentelement 112 downwardly and also the shaped parts 116 with the abutmentelement 112 via the ring-like collar 120, the maximum downward movementof the shaped ‘parts is bounded by the upper side 134 of the ringshoulder against which the shaped parts enter into contact. This alsorestricts, via the collar 120 and the grooves 122, the lowest possibleposition of the abutment element 122. The upper end 136 of the abutmentelement 122, which can be seen in enlarged form in FIGS. 8 and 9, formsa shaping space 138 for the tubular end 14 of the spherical bolt element10. This ring-like shaping space has a rolling surface 140 ofsemicircular ‘shape in cross-section in its base region which isarranged significantly below the radially inwardly projecting noses 142of the shaped parts 146. The end face 143 of the central post 144 of theabutment element lies flush with the upper side 146 of the shaped partsin FIG. 8, which in turn lies flush with the upper side of the outerpart 106 of the die 104 and of the tool (not shown), which accommodatesthe die.

The reference numeral 150 points to a ring spring element which holdsthe shaped parts to the abutment element.

As evident from FIG. 8 the shaped parts have rounded edges 152, which isevident from the double line execution.

Whereas, in the die, in accordance with the PCI ApplicationPCT/EP00/06468 the sheet metal part is shaped into a pot-like recessduring the stamping of the corresponding element into a shaping space ofthe die, the central post 144 cooperates with the piercing and rivetingfeatures 28, 30 of the lower end of the spherical bolt element 10 inorder to punch out from the sheet metal part a punching slug 44 similarto the manner described for the shaping die of the German Patent DE-PS34 47 006.

The lower end face 24 of the spherical bolt element punches through thesheet metal part 18 in collaboration with the upper end 143 of thecentral post of the abutment element 12 and draws the sheet metal partaround the hole which is formed in this way over the rounded noses 142of the shaped parts into the shaping space 138 of the die. At the sametime the material of the tubular end of the spherical bolt element 10 isdeflected radially outwardly, and then upwardly again, by the rollingsurface of the abutment element of the die until the free end 24 of thespherical bolt element 10 abuts against the underside 154 of theradially inwardly projecting noses 142 of the shaped parts 116.

One can see from FIG. 9 that the conical shape 156 of the sheet metalpart 18 in the shaping space 130 of the die now lies in form-fittedmanner within the turned over end 14 of the spherical bolt element 10and in that at least essentially the entire shaping space 138 is full ofmetal. As soon as this position is achieved the material of thespherical bolt element can no longer flow into the shaping space 138,the length of the tubular collar is, however so dimensioned that thepreviously mentioned ring fold 40 can form, which is shown in FIG. 9.The movement of the free end 24 of the spherical bolt element iseffectively stopped at the lower side 154 of the noses of the shapedparts 116, so that the ring fold 40 can now be formed.

One notes that the punching slug 44 which arose on punching through thesheet metal part is trapped between the upper end 143 of the centralpost 144 and the transverse wall 66 inside the hollow space 26 and therestiffens the connection to the sheet metal part.

During opening of the press after the punching in of the spherical boltelement 10 the spherical bolt element is first lifted and simultaneouslylifts the sheet metal part to which it is now attached, out of the die.In doing so the shaped parts 116 jointly lift upwardly, together withthe abutment element 112, with the coil spring in the hollow space 126being compressed until the forces which act in the region of the rivetbead 36 are sufficient to press the shaped parts 116 radially outwardlyaway from the rivet bead 36, whereby the component assembly consistingof the spherical bolt element 10 and the sheet metal part 18 are freedfrom the die 104.

The upper part 160 of the tool 104 of FIG. 7 represents a setting headwhich is designed for the attachment of the spherical bolt element suchas 10 to the sheet metal part 18 and for this purpose can be attachedvia a holder, not shown, to an upper tool 163 of a press or to anintermediate platen of a press or, in an inverse arrangement, to a lowertool of the press.

The setting head 160 is aligned here in order to achieve a centralalignment of the spherical bolt element with the die and prevents akinking of the bolt element when it is stamped into place. The dieensures a termination of the beading operation when the free end face 24of the rivet bead 36 runs against the die insert, i.e. against theshaped parts 116 and thus a defined starting point for the bulging outof the shaft 16 for the formation of the ring flange 40 and indeed evenwhen only one shaped part 116 is provided, which is fundamentallypossible with a die construction similar to the EP application 00 931155.6.

The setting head 160 has an outer tubular part 162 with a conical recess164 at the lower end 166 in which, in turn, a plurality of shaped parts,for example four shaped parts 168, are accommodated of which only theone shape part 168 is visible in FIG. 7. The shaped parts each have aconical outer wall 170 which is made complementary to the conical wall164 of the outer part 162 of the setting head 160.

In the lower region of the shaped parts in FIG. 7 these have radiallyinwardly extending jaw faces 172 which engage on the shaft part 14 ofthe spherical bolt element 10 and are formed as part-cylindricalsurfaces so that an areal contact at the spherical bolt element ispossible, in order to ensure the required alignment of the sphericalbolt element 10 with the central longitudinal axis 174 of the settinghead, which stands coaxial to the central longitudinal axis 118 of thedie.

In the upper region the shaped parts 168 have radially inwardly directednoses 176 which extend into a groove 180 in a displaceable sleeve 182 ofthe setting head 160. The lower boundary 184 of the groove engages behind the noses so that the shaped parts 168 are compulsorily guided,i.e. axially movable with the sleeve 182.

A ring spring 184 surrounds the shaped parts 168 and thus ensures thatthe shaped parts. 168 are not lost. The sleeve 182 has in its upperregion a radially outwardly directed collar 186 which is movable in acircularly cylindrical hollow space 188 of the outer part 162 of thetool 160, with a radially inwardly directed ring shoulder 190 of theouter part 162 of the tool 160 bounding the hollow cavity 188 at thebottom and forming an abutment for the radially outwardly directedcollar 186 of the sleeve 182.

Within the upper region of the sleeve there is located a lightcompression coil spring 192, the lower end 194 of which contacts aradially inwardly directed shoulder 196 of the sleeve 182 and the upperend of which in FIG. 7 is braced against the upper tool 163 of thepress. In this embodiment the spring thus lightly biases the sleeve inthe direction radially downwardly.

A plunger pin 200 with a conical upper end 202 is located within acylindrical bore 198 of the sleeve 182 in the lower region of the sleeveand is supported against a corresponding conical surface within thedisplaceable sleeve 182, so that the plunger pin 200 cannot falldownwardly out of the sleeve 182. Above the plunger pin 200 there is agrub screw 204 which is screwed into a threaded bore 206 of thedisplaceable sleeve to prevent the plunger pin 200 deviating upwardly.The screw connection between the grub screw 204 and the sleeve 182ultimately also transmits the pressure forces, which coming from theupper tool 163 of the press, press the sleeve 182 and thus also the grubscrew 204 and the plunger pin 200 downwardly. One can see that theplunger pin 200 comes into contact on the flat 84 at the upper end ofthe spherical bolt element 10.

On closing the press the spherical bolt element cannot deflect upwardlyand the downwardly directed forces lead to the above described piercingof the sheet metal part and also to the shaping of the lower end 14 ofthe spherical bolt element 10 and the formation of the ring fold 40.When these shaping operations are concluded the lower end 16 of theupper tool 160 contacts the sheet metal part 18 and presses the latteragainst the lower tool in the form of the die 104.

On opening of the press the upper tool 160 lifts the spherical boltelement 10 with the attached sheet metal part 18 out of the die so thatthe die releases the component assembly, as described above. The sheetmetal part then strikes against other parts of the press (not shown) sothat a downwardly acting force is exerted on the spherical bolt element.The spherical bolt element thus pulls the shaped parts partly out of theouter part of the upper tool to such an extent that the outwardlyextending collar 186 comes into contact with the radially inwardlydirected ring shoulder 190. This axial movement is sufficient in orderto release the spherical head from the shaped parts 168 since these candeflect radially outwardly when they are partly pulled out of the outerpart of the upper tool. In order to favour this radially outwardlydirected movement the shaped parts 168 have in the region of the axialupper ends of the jaw surfaces 172 inclined faces or shaped faces 208which cooperate with the rounded spherical surface of the spherical headof the spherical bolt element.

The component assembly comprising the spherical bolt element and thesheet metal part can now be removed from the working area of the tool inaccordance with FIG. 7.

Since the compression coil spring holds the shaped parts in the openedposition a new spherical bolt element can be introduced from below intothe upper tool and pressed upwardly (until the jaw surfaces 172 of theshaped parts again engage the shaft part 14 of the spherical boltelement 10 and the compression coil spring is compressed. The ringspring 205 which, for example consists of polyurethane and which pressesthe shaped parts 168 towards one another is made sufficiently strong tohold the sleeve 182 with the shaped parts 168 in the position shown inFIG. 7 by friction at the conical wall 164. The new spherical boltelement now adopts the position of the spherical bolt element 10 of FIG.7.

A new sheet metal part 18 can now be introduced into the press and, asdescribed previously, the new spherical bolt element can then be rivetedto the new sheet metal part 18.

Instead of inserting the bolt element from below, for example by hand,between the shaped parts or shaped segments 168 of the upper tool thespherical bolt elements 10 can be introduced in an automated embodimentthrough an obliquely aligned guide channel 210 into the space betweenthe shaped parts.

If for example three shaped parts 168 are provided, the obliquelyaligned guide passage can lead into the intermediate space between twoof the segment-like shaped parts 168. This makes it possible for thespherical bolt element 10 to move from the obliquely aligned position ofthe guide passage 210 into the vertically aligned position between theshaped parts 168. A similar procedure is however also possible if thetool 160 is pro vided with four contacting shaped parts 168, providingthe necessary space for the guide passage 210 can be created.

The series of sketches 10A, 10B, 10C and 10D finally show that it isalso possible to insert the spherical bolt element into thicker piecesof sheet metal. With sheet metal of approximately 1.5 mm thickness it issufficient to pierce the sheet metal part 18 or, as is shown in FIG.10A, to pre-form a hole as at 212.

For sheet metal thicknesses beyond 1.5 mm it is however favourable tocarry out a sheet metal preparation step so that the sheet metal has theshape of FIG. 10B in the region of the hole 214. A sheet metalpreparation of this kind is for example described in connection with theso-called clamping hole riveting process (European Patent 539 793) andin connection with the so-called EBF elements in the PCT ApplicationPCT/EP96/04188, which is why it is not repeated here. FIG. 10C showsthat the inner diameter of the hole 215 corresponds during the preforming of the hole and preparation of the sheet metal part at leastsubstantially to the outer diameter d of the lower end 14 of thespherical bolt element. FIG. 10D finally shows the position after theattachment of the element which is executed according to the PCTApplication PCT/EP00/06465.

The possibility also exists of using the die of FIG. 7 to attach thebolt element into the prepared sheet metal part, with no punching slugarising here because the sheet metal part is not pierced by thespherical bolt element. The installation situation presents itselfsimilarly to that of FIG. 10D except that a nip is present between thebeaded over end 24 of the rivet bead 36 and the sheet metal part whichis produced by the noses 142 of the shaped parts 106 of the die 104.

In a further embodiment, the invention relates to a functional elementcomprising a shaft part and a head part designed for a riveted joint toa panel member, in particular to a sheet metal part, and a method ofinserting the functional element into a sheet metal part and a componentassembly comprising the functional element and the sheet metal part.

A functional element of the kind first mentioned is known, for example,from German patent 34 47 006 and is realized there as a threaded stud,with the head part being provided with a tubular piercing and rivetingsection which is designed to pierce a sheet metal part and tosubsequently form a rivet flange, whereby the element is fastened in thesheet metal part. The head part has a flange between the tubularpiercing and riveting section with an annular surface which isperpendicular to the longitudinal axis of the element and which isnormally arranged just below the side of a sheet metal part adjacent tothe shaft part after the insertion of the element into a sheet metalpart.

The panel slug formed in the piercing of the sheet metal part is pressedinto the piercing and riveting section and thus supports the rivetedjoint to the sheet metal part. DE PS 34 47 006, however, also describesfunctional elements in the form of nut elements, where the shaft part isto be under stood as an extension of the head part and this is providedwith a female thread. However, the shaft part does not have to berealized as a thread; many embodiments are possible, for example a guidespigot or a pin-like design to which, for example, carpets can be fastedby means of corresponding clips.

Such functional elements, i.e. in accordance with DE PS 34 47 006 C2,have proved themselves over many years and allow the production of ahigh-quality joint between the element and the sheet metal part. Suchelements are, however, relatively costly in production and sometimesrequire the use of extremely precisely operating cold forming machineswhich work relatively slowly to obtain the desired quality. The need touse relatively expensive cold forming machines and the limited operatingspeed lead to relatively high production costs. Furthermore, it would bemore favourable for some applications if the weight of the elementscould be reduced.

It is the object of the present invention to provide functional elementswhich can be manufactured very economically and at a favourable cost,which preferably have a lower weight than comparable elements of theinitially named kind and which also have an acceptable resistance topull-out or twist-out for many purposes.

In accordance with a first embodiment for the satisfying of this object,provision is made in accordance with the invention that at least thehead part of the element is made hollow and has at least substantiallythe same outer diameter as the shaft part. The element therefore has noflange between the head part and the shaft part. It is furthermorepossible in accordance with a second version of the invention to makethe head part with a larger or smaller diameter than that of the shaftpart, with a transition taking place with a change in the diameterbetween the head part and the shaft part, but with no flange part in theconventional sense being present.

The function of the flange part in the known elements is, on the onehand, to provide a sufficient area which prevents the element frombecoming loose in the sheet metal part and, on the other hand, also toform a surface on which further sheet metal parts or other componentscan be fastened, for example, if the element in question is a boltelement, by a nut which is screwed onto the shaft part of the functionalelement having a thread.

In the functional elements in accordance with the invention, this flangeis initially not present on the actual functional element. When thefunctional element is inserted into the sheet metal part, the end of thefunctional elements pierces the sheet metal part, as with the elementsknown per se, and formed into a rivet flange on the side of the sheetmetal part remote from the shaft part of the element. Subsequently, thefunctional element is compressed in the longitudinal direction such thata part of the hollow head part is formed into an annular fold or annularbulge which now serves as a flange and assumes the functions of theconventional flange described above.

As the head part in the functional element has at least substantiallythe same outer diameter as the shaft part, the demands on manufacturingit as a cold formed part are substantially lower than with themanufacture of a head part with a flange whose diameter is substantiallylarger than that of the shaft part. Thus, lower priced cold formingmachines with a faster operation can be used, whereby the productioncosts can be cut.

Furthermore, the functional element cannot only be manufactured in aneconomic manner by cold forming, but also by high-pressure formingmethods from lengths of tubing. Moreover, a variety of other, lowerpriced manufacturing procedures are possible. Although only a hollowhead part is necessary for the attachment of the part to a workpiece,the functional element can easily be manufactured overall as a tubularpart. A manufacture with a larger inside diameter in the hollow headpart than in the shaft part can also be realized at favourable cost,particularly when a tube is used as the starting material.

As indicated above, in the present invention, the actual flange is onlyformed at a later point. As the sheet metal part is clamped in aform-locked manner within a relatively large-area mount between therivet flange on the one hand and the annular fold on the other, thefunctional element in accordance with the invention has a goodresistance to twisting. The embodiment in which the panel slug isclamped inside the rivet flange increases the security against rotationeven further and also in creases the resistance to being pulled out.

Should it be necessary to increase the security against rotation evenfurther, this can be done in a number of different ways. On the onehand, smaller features providing security against rotation, such asgrooves or noses, can be provided in the region of the head part formingthe rivet flange; on the other hand, radially extending noses can beprovided either in the die to form the rivet flange and/or in the endface of the plunger forming the annular fold which then also lead to ajoint deformation of the sheet metal part and the adjoining regions ofthe rivet flange and/or the annular fold which serve to increase thesecurity against rotation. It is also possible to equip the surface ofthe annular fold with sharp, radially extending noses or the like whichprovide an electrical contact to a connecting terminal. Such noses canbe provided either on the outer surface of the head part before theinsertion of the element or formed or embossed in the exposed surface ofthe annular fold only subsequently when the annular fold is formed.

Particular advantages and preferred embodiments of the functionalelement and of the method of inserting the element into a sheet metalpart, of the component assembly made in this way, of the die used tomanufacture the component assembly and of the plunger arrangement usedcan be seen from the claims and the following description.

The invention of the further embodiment is described in more detailbelow by way of embodiments and with reference to the enclosed drawingin which are shown:

FIG. 11 a view, partially cut away in the longitudinal direction, of afunctional element in the form of a bolt element;

FIG. 12 the first step in the insertion of the functional element into asheet metal part;

FIG. 13 an intermediate stage in the insertion of the functional elementinto a sheet metal part;

FIG. 14 the end of the insertion method prior to the opening of thepress or caliper used therefor;

FIG. 15 a partially cut-away view of the finished component assembly,i.e. the result after the end of the method step in accordance with FIG.14;

FIG. 16 a representation of a functional element with a head part havinga greater diameter than that of the shaft part;

FIG. 17 the element of FIG. 16 in the assembled state;

FIG. 18 a representation similar to FIG. 16, but where the head part hasa smaller outer diameter than the shaft part;

FIG. 19 the functional element of FIG. 18 in the assembled state;

FIG. 20 a representation similar to FIG. 11, but at a larger scale andof a hollow element;

FIG. 21 a view, partially cut away in the longitudinal direction, of afurther functional element in accordance with the invention in the formof a nut element;

FIG. 22 the nut element of FIG. 21 in the assembled state;

FIG. 23 a functional element partially cut away in the longitudinaldirection which is made as a pin to receive a spring clip;

FIG. 24 shows in FIGS. 24B, 24C and 24D a modified setting head designedfor the insertion of the tubular element in accordance with FIG. 24Ainto a sheet metal part in such a way that no damage to the threadcylinder need be feared, with FIG. 24E showing the completed componentassembly;

FIG. 25 shows a further embodiment of an element in accordance with theinvention similar to that of FIG. 11, also in a representation partiallycut away in the axial direction, with this element being used in thefollowing description of the die and process technology preferred inaccordance with the invention in accordance with FIGS. 26 to 28;

FIG. 26A an axial section through a die in accordance with theinvention;

FIG. 26B an end view of the die of FIG. 26A seen in the direction ofarrow B;

FIG. 27 a sequence of drawings in which FIGS. 27A to 27H show the methodpreferred in accordance with the invention of attaching the functionalelement in accordance with the invention and using the die preferred inaccordance with the invention, with FIG. 27I illustrating the completedcomponent assembly in a partially cut-away form;

FIG. 28A to FIG. 28C a preferred embodiment of the plunger arrangementin accordance with the invention which is preferably used in the methodin accordance with FIG. 27;

FIG. 29 a partially cut-away view to illustrate the attachment of anelement in accordance with the invention to a sandwich-like component,the element and the component being shown prior to the attachment of theelement on the left side of the central longitudinal axis and after theattachment of the element on the right side of the central longitudinalaxis; and

FIG. 30 a schematic representation similar to that of FIG. 29, but witha modified kind of sheet metal preparation.

The functional element 10 of FIG. 11 comprises a shaft part 24 providedwith a male thread 12 and a hollow head part 16 having at leastsubstantially the same outer diameter as the thread cylinder of theshaft part 14. The male thread 12 shown here is a rolled thread, i.e.the thread formation has been effected by rolling.

A circularly cylindrical hollow space 18, which is located within thehollow head part 16, leads from the end 20 of the head part 16 remotefrom the shaft part 14 up to directly below the thread cylinder and endsthere in a transverse wall 22. The hollow space 18 here has the form ofa bore. The shape of the transverse wall 22 corresponds to the base of abore made with a twist drill, although the hollow space 18 and thetransverse wall 22 do not necessarily have to be made with a twistdrill, even though this does represent one possibility. The hollow spaceand the transverse wall could, for example, be made by means of a coldforming process. The longitudinal axis of the functional element 10,which is realized here as a bolt element, is designated with 24.

The element 10 is made at the end 20 exactly like the corresponding endof the piercing and riveting section of the functional element inaccordance with DE PS 34 47 006 C2, i.e. it has an inner cutting face 26and an outer, rounded off punching and drawing edge 28.

In FIG. 11, the cutting face 26 is made very small. As a rule, it is,however, 10 made in accordance with the conical cutting face 426 of theembodiment in accordance with FIG. 21.

FIGS. 12, 13 and 14 now show three different stages in the insertion ofthe functional element 10 in accordance with FIG. 11 into a sheet metalpart 30.

The insertion method is described in more detail below with reference tothe further FIGS. 25-28, which represent the currently preferredembodiment in detail. The present description is intended as anintroduction for a knowledgeable reader.

As is shown in FIG. 12, the sheet metal part 30 is supported at thebottom on a die 32 which is equipped with a centrally disposedcylindrical plunger projection 34 which is designed in accordance withthe plunger projection of the corresponding die in accordance with DE PS34 47 006 C2. This plunger projection is surrounded by a rounded annulardepression 36 which merges into an annular recess 40 of a largerdiameter at the end face 38 of the die remote from the sheet metal part30. The die 32 is over all very similar to the die 180 described in DEPS 34 47 006.

The die 32 is located in a lower tool of a press (not shown). The sheetmetal part is clamped against the end face 38 of the die by a, forexample, tubular hold down member, which is not shown, but which isarranged concentrically to the cylindrical outer plunger 42 of thesetting head 44. That is, the sheet metal part 30 is clamped tightoutside the annular recess 40. The shaft part of the functional element10 is located in the cylindrical guide passage 46 of the setting head44, while the head part 16 projects out of the cylindrical outer plunger42. An inner plunger 48, which presses onto the end 29 of the shaft part12, is arranged within and concentric to the tubular outer plunger 42.Although the inner plunger 48 can be drawn back with respect to theouter plunger for the insertion of the respective functional elements,the relative position of the inner and outer plungers 48, 42 remainsconstant for the process steps in accordance with FIGS. 12, 13 and 14.The same applies to the apparatus to be described below.

In the stage of the process step in accordance with FIG. 12, the endface 20 of the functional element has pressed the sheet metal part intothe annular recess 40 of the die 32 under the pressure of the innerplunger 48 and drawn a shallow, approximately conical recess in thesheet metal part 30. In the stage of FIG. 12, the plunger projection 34in cooperation with the cutting surface 26 at the end of the head part16 of the functional element 10 has cut out a panel slug 50 from thesheet metal part.

It can be seen from FIG. 13 that the plunger arrangement 43 comprisingthe inner plunger 48 and the outer plunger 42 has traveled further downwards, with the free end region of the hollow head part of the element10 being formed into an annular rivet flange 37 around the downwardlydrawn rim of the aperture of the sheet metal part as a result of therounded annular depression or roll surface 36 in the die. The hole inthe sheet metal part has a marginal region in this stage of the processwhich is similar to the mouth of a trumpet.

In the continued course of the joint downward movement of the innerplunger 48 and the outer plunger 42, the cylindrical wall of the headpart 16 is compressed in the region directly beneath the shaft part 14such that an annular fold 52 is formed, as can be seen from FIG. 14. Theconstraints to which the element is subjected due to the guiding by theouter plunger 42 on the one hand and due to the punched edge and thepanel slug on the other ensure that the deformation takes place as shownin FIG. 14.

It can be seen from FIGS. 12 and 13 that the outer plunger 42 has anannular nose 56 at its end 54 with a face extending perpendicular to thelongitudinal axis 24 of the functional element. This annular nose 56,which is not absolutely necessary, presses on the annular fold in themethod stage in accordance with FIG. 14 and ensures that a clear fold ismade here so that the material of the wall of the head part is foldedlike a hair grip, i.e. through 1800, and the two layers of materialformed in this way fully contact one another. Furthermore, the annularnose ensures that the annular surface 57 of the ring fold formed in thisway lies slightly below the plane of the sheet metal part 30. The ringflange 52 formed in this way now has the function of a flange which wasalready present in the starting stage in the elements previously known.It is also ensured by the annular nose 56 that the material package iscompressed in an axial direction in the region of the form-locked jointof the hollow head part 16 of the functional element to the sheet metalpart 30 and is thus made in an extremely stable and strong manner.Optionally, the annular nose 56 can be equipped with forming featureswhich, on the one hand, lead to a selected, interlocked arrangementbetween the sheet metal part 30 and the hollow head part 16 whichpromotes the security against rotation and which, on the other hand, canalso be designed in such a way that, for example, noses are created inthe upper annular surface of the annular fold of FIGS. 14 and 15 whichensure a high-quality electrical contact, for example when thefunctional element is used as a ground connection element. As analternative or supplement to this type of realization of the securityagainst rotation, the element can also be bonded to the sheet metal partby means of an adhesive. For example, the functional element 10 can becoated with a pressure-sensitive adhesive in the region of the head part16 which is only activated under pressure when the functional element isattached to the sheet metal part.

In the stage of FIG. 14, the insertion of the functional element 10 intothe sheet metal part 30 is complete. The press opens and the componentassembly produced in this way then has the shape visible from FIG. 15.

In this description, it is initially assumed that the die 32 is a diewhich is arranged in the lower tool of a press. In this case, thesetting head 44 is fastened either to the upper tool of the press or toan intermediate plate of the press. The die 32 can, however, equally bearranged on the intermediate plate and then cooperate with a settinghead which is arranged on the lower or upper tool of the press. It isequally possible to attach the die 32 to the upper plate of the tool andto mount the setting head to an inter mediate plate or to the lower toolof the press. Furthermore, the setting head 44 and the die 23 can bepressed onto one another by a robot or be brought together by otherdevices.

The further FIGS. 16 to 23 now show different possible aspects of thefunctional element in accordance with the invention and are described inmore detail below. In all following examples, the same referencenumerals are used as for the embodiment of FIGS. 11 to 15, but increasedfor each embodiment successively by the base number 100 for clearidentification. It is, however, understood that features characterizedby the same two last numerals always have the same or a correspondingfunction as in the embodiment in accordance with FIGS. 11 to 15. Suchfeatures are only de scribed separately if a different aspect has aspecial importance.

FIG. 16 shows that it is not absolutely necessary for the head part 116of the functional element 110 to have the same diameter as the shaftpart 114. The hollow head part in FIG. 16 has a larger diameter than theshaft part 114. Here, too, the functional element 110 does not have anactual flange in the starting state. The flange is rather only formedduring the insertion of the functional element 110 into a sheet metalpart, as is described in connection with the first embodiment inaccordance with FIGS. 11 to 15 and shown in FIG. 17.

FIG. 17 now shows the functional element 110 of FIG. 16 in the assembledstate. It can be seen clearly here that the annular fold 152 forms aflange as in the embodiment in accordance with FIG. 15.

In the embodiment of FIG. 18, the head part 216 has a smaller outerdiameter than the outer diameter of the thread cylinder of the shaftpart 214 of the functional element 210. The functional element 210 insuch an embodiment also initially lacks a flange which contacts thesheet metal part. A flange is nevertheless formed into an annular fold252 during the insertion of the functional element into a sheet metalpart due to the compression of the hollow head part 216, as can be seenfrom FIG. 19.

FIG. 20 now shows that the functional element 310 can also be made intubular form. The functional element 310 of FIG. 20 is actually made sothat the shaft part 314 is also hollow. Such a functional element hasthe special advantage that it can be made without problems from atubular section, with the expansion shown in FIG. 20 of the bore B ofthe tube in the region of the hollow space 318 being able to be madewithout any problem, for example either during cold forming or in ahigh-pressure forming procedure inside a corresponding outer mould. Themale thread 312 of the functional element 310 of FIG. 20 can, as in theother prior examples, be produced in a generating process; however itcan also be made by a high-pressure forming process inside a mould. Thusthe male thread shown here is a compression formed thread, i.e. has beenmade by compression forming. This is possible due to the use of atubular section or part of a tubular section as the starting material,as the required internal high pressure can be introduced without problemin all longitudinal regions of the tube or in a tube lengthcorresponding to the length of the functional element via thecontinuously hollow internal space of the tube.

In the state fitted into a sheet metal part, the form-locked joint ofthe head part 316 to the sheet metal part corresponds to the previousembodiment in accordance with FIG. 15.

FIG. 21 shows a further embodiment version similar to the embodiment ofFIG. 20, but in this case the element is provided with a female thread412.

FIG. 22 shows the assembled state of the functional element inaccordance with FIG. 21. It can be seen that the hollow head part 416 isdeformed in exactly the same way as in the prior embodiments—with thedifference that in this case the upper annular surface 457 of theannular fold 452 is arranged a little above the sheet metal part.However, this is not absolutely necessary. The corresponding surfacecould equally well be arranged beneath the plane of the sheet metal part430 or at the same height as the plane of the sheet metal part.

It can also be seen in FIG. 22 that the panel slug 450 closes thecentral passage of the hollow functional element 410 in the region ofthe rivet flange 437 so that a sealing is performed at this point. Thepanel slug can, however, also be removed.

The embodiment in accordance with FIG. 22 then has the particular advantage that a bolt element (not shown) can be screwed into thefunctional element 410 from below. In this way, the annular fold and therivet flange and the material of the sheet metal part 430 clampedtherebetween are drawn even tighter together when the bolt is tightened,with the large contact surface 480 of the annular fold forming a verystable connection. In the event that the functional element 410 is to beused with such a bolt, the panel slug 450 is pressed into and removedfrom a central passage of the die, for example, by means of a leadingpiercing plunger. The removal of such a panel slug in this manner isalready known. The leading piercing plunger is used to pre-pierce thesheet metal part in such cases.

The die is then made in a known manner such that it only deforms thefree end of the hollow head part around the correspondingly deformedsheet metal part. That is, the die is made provided with a central holeinstead of with a plunger projection such as 34 in FIG. 12. The slugcan, however, also be ejected in a subsequent operation, when theelement is inserted as shown in FIG. 12.

FIG. 23 shows a functional element 510 which is also made in tubularform, but which has no thread. The functional element instead has aperipheral groove 560 which is intended to receive a spring clip (notshown). It can also be seen that the free end 529 of the functionalelement 510 of FIG. 23 is made in a conical shape. The correspondingspring clip can be pressed downwards over this conical surface and thensprings into the groove 560.

The functional element 510 of FIG. 23 can be inserted in this or in aslightly modified form (for example without the peripheral groove 560)into a sheet metal part and be used either as a pin or as a cylindricalspigot. It could also be used with a thread-forming screw which shapesor cuts a thread itself when screwed into the completed componentassembly in the hollow shaft part 514 of the functional element 510. Inthe embodiments of FIGS. 20, 21, 22 and 13, the hollow head part 316,416, 516 can easily have a larger or smaller diameter than the outerdiameter of the corresponding shaft part 314, 414, 514.

In the embodiments with a hollow shaft part, the inner plunger 48 canoptionally be guided into the hollow internal space of the shaft part tostabilize the functional element during the compression procedure. Thisprocedure, which also has an advantageous effect on the formation of theannular fold, is shown in FIG. 24 in the drawings 24B, 24C and 24D. Forthis purpose, the inner plunger 648 has a journal-like projection 649with a diameter corresponding to the inner diameter 651 of the hollowshaft part 614, with the projection 649 merging into the upper part ofthe inner plunger via an annular shoulder 653 which presses onto theannular end 629 of the shaft part.

The outer plunger 642 of the plunger arrangement 643 in accordance withFIGS. 24B to 14D can be provided with a circular cylindrical bore whosediameter corresponds to the diameter of the external thread 612 of theshaft part 614, approximately as shown in FIGS. 24C and 24D.

Despite the spigot-like projection 649 of the inner plunger 648, withsuch an arrangement it is, however, possible under certain circumstancesthat the thread cylinder is damaged and/or that the thread cylinder iscorn pressed. The double arrows of FIG. 24B indicate a possible remedy.This remedy consists of the outer plunger 642 being divided into atleast two segments which, corresponding to the double arrows 655, can bemoved radially away from the element 610 into position 657 in which theydo not impair the insertion of the element 610 through the plungerpassage 646 of the setting head. These segments, of which there may betwo, three or more and which then have a corresponding angular extent(for example 180°, 120°, etc.), can be provided on their radially innersides with a shape 659 matching the thread cylinder 612 so that, duringa closing movement of the segments of the outer plunger in a directionradially towards the longitudinal axis 624, the thread segments of thecorresponding thread 659 engage the thread of the thread cylinder 612and in this way serve to transmit axial forces to the element 610 on theone hand and, on the other hand, prevent any compression of or injury tothe thread cylinder 612 from occurring. For this purpose, the design ofthe thread segments 659 is selected complementary to that of the threadcylinder 612.

After the attachment of the element in accordance with FIG. 24D, thesegments of the outer plunger 642 are then moved apart again, that is ina direction radially outwardly away from the longitudinal axis 624, sothat the outer plunger 642 can travel upwards for the removal of thecompleted component assembly in accordance with FIG. 24E without thethread cylinder being damaged thereby.

The concept of the radial movement of segments of the outer plunger 642will be described in more detail below with reference to a preferredembodiment in accordance with FIG. 28.

FIG. 25 now shows a functional element 710 which is very similar to thefunctional element 10 of FIG. 11 and which basically only differs fromthis in that the base of the hollow space 718, which forms thetransverse wall 722, is made only slightly concave here instead ofconical and extends substantially perpendicularly to the longitudinalaxis 724 of the element 710 and merges into the cylindrical outer wallof the head part 716 of the element 710 via a generous radius 723. Whilethis shape of the base forming the transverse wall 722 is not absolutelynecessary, it does lead to a more high quality support of the shaft partin a practical example, which serves the stability of the connection.

FIGS. 26A and 26B show the die which is preferably used to insert thefunctional element 710 of FIG. 25. While this die 732 is similar to thedie in accordance with FIG. 12, it does show certain differences. Forinstance, the plunger projection 734 in this embodiment is extendedaxially upwards in the direction of the longitudinal axis 724 so thatthe flat face 735 of the plunger projection 734 projects slightly abovethe end face 733 of the die.

This embodiment has the advantage that while the functional element isstill made with a conical cutting surface 726, the face 720 of the headpart 716 is made simply as an annular surface which is perpendicular tothe longitudinal axis 724 and which is not rounded as, for example, atthe rounded portion 28 in FIG. 11. A manufacturing step is saved in thisway in the manufacturing of the functional element. The annular recess740 of the die 732 is in principle of similar design to the annularrecess 40 of the die 32 in accordance with FIG. 12, but is roundedconvexly at the transition into the end face 733, as shown at 737.Furthermore, a plurality of inclined grooves 739—in this embodimenteight such grooves, as shown in FIG. 26B—are worked into this roundedtransition 737 so that radially extending noses 741 are in each caseformed between two adjacent grooves 739.

The grooves 739 are at least substantially semi-circular in shape incross section and well rounded, like the noses 741 therebetween, so thatwhile they do deform the sheet metal part, they do not injure it. Thesegrooves 739 and noses 741 serve to increase the security againstrotation of the element with respect to the sheet metal part.

FIGS. 27A to 27H now show the die 732 in accordance with FIG. 26, whichis used to attach the functional element 710 to a sheet metal part 730using a plunger arrangement 743.

The die 732 is here located in a bore 760 of a lower tool 762 of a presswhose upper side 764 is arranged flush with the face 733 of the die. Aplurality of tappets 768 upwardly biased by spring 766 are located inthe lower tool 762 and support the sheet metal part 730 during theinsertion into the press, but can be pressed downwardly due to the forceexerted by the hold down member 770 when the press is closed so that thesheet metal part 730 comes into contact with the end face 733 of the die732 and with the upper side 764 of the lower tool in the region of thedie and is immovably clamped there between the hold down member 770 andthe die 732 or the lower tool 762.

Three such spring-biased tappets 768, for example, can be provided whichare arranged, for example, at equal angular intervals around the centrallongitudinal axis of the die 732, with only one tappet 768 being visibledue to the sectional drawing. The central longitudinal axis of the dieis simultaneously the central longitudinal axis 724 of the functionalelement 710, that is it is aligned therewith.

The hold down member 770 is also biased in the direction of the sheetmetal part by springs 772 which here—like the spring 776—are indicatedschematically as compression coil springs, although other spring typescan also be used which are well known in tool-making. The hold downmember 770 can belong to a setting head having the plunger arrangement743 or to a tool of the press on which the setting head is fitted. Theupper ends of the springs 772 are accordingly braced against the settinghead or the tool.

In this example, three springs 772 are also arranged at equal angularintervals around the central longitudinal axis 724 so that the hold downmember 770 is pressed evenly downwards under the force of these springs.

FIG. 27A shows the state after the sheet metal part 730 has beeninserted 10 into the press and the closing movement of the press hasbeen begun—just so far that the hold down member 770 contacts the upperside of the sheet metal part and lightly clamps the sheet metal partbetween it and the tappet 768.

The plunger arrangement 743 here also comprises an outer plunger 742 andan inner plunger 748, with the lower end 774 of the inner plunger 748pressing onto the upper face 729 of the functional element 710. It canbe seen that the head part 716 of the functional element 710 projects atleast substantially completely from the outer plunger 742, with thetransverse wall 722 forming the base being arranged only slightly abovethe lower face 776 of the outer plunger 742. The shaft part 714 of thefunctional element 712 is, in contrast, located completely inside theouter plunger 742.

It can be assumed in this representation that the lower tool 762represents the lower tool of a press while the setting head is fixed inthe upper tool of the press or on an intermediate plate. Differentarrangements are also feasible which were described at the end of thedescription of FIG. 15.

As the press continues to close, the spring hold down member 770 ispressed so hard against the sheet metal part 730 that this presses thespring tappets 768 downwards until the sheet metal part 730 is nowclamped firmly and immovably between the hold down member 770 and thelower tool 762 or the face 733 of the die. In this example, a furtherdownward movement of the hold down member 770 is not planned. The uppertool of the press or the intermediate plate of the press can, however,be moved further downwards in accordance with the further closingmovement of the press, whereby the compression coil springs 772 arefurther compressed, without the hold down member 770 changing itsposition.

In this further closing movement of the press, the outer plunger 742 isalso pressed so far down together with the inner plunger 748 in thestage of FIG. 27B that the lower end 720 of the functional element 710has just cut a panel slug 750 out of the sheet metal part 730 incooperation with the plunger projection 734 of the die 732.

It can be seen that the inner diameter of the shaft part 716, that isthe diameter of the hollow space 18, is only slightly larger than theouter diameter of the plunger projection 734. It can further be seenthat the lower end 720 of the functional element 710 has pressed themarginal region 778 of the aperture of the sheet metal part 730 createdby the separation of the panel slug 750 into the annular depression 732of the die under the pressure of the plunger 748 so that this marginalregion 778 forms a conical recess in the sheet metal part 730.

In the further closing movement of the press in accordance with FIG.27C, the marginal region 778 of the aperture created by the removal ofthe panel slug 750 is pressed even further into the annular depression736, with the end 720 of the functional element 710 having just reachedthe U-shaped base region of the annular depression 736 and just beingabout to be deformed radially outwardly by the shape of this baseregion.

This deformation is then continued during the further closing of thepress in accordance with FIG. 27D so that the end 720 is now rolledannularly outwards and engages round the lower end of the marginalregion 778, whereby the rivet flange is now being created. During thisfurther closing movement of the press, the panel slug 750 is alwayspushed further axially into the shaft part 716 of the functional element710. As the press continues its closing movement, in the state of FIG.27E, the cylindrical wall of the shaft part 716 now begins to beexpanded radially outwards in the region inside and above the marginalregion 778 of the sheet metal part 730 and beneath the transition to theshaft part 14, so that the wall of the head part in the region of theface 735 of the plunger projection 734 begins to move away therefrom ina radial direction. The panel slug 750 is displaced further in thedirection towards the shaft part 14 of the functional element 710.

As the press continues the closing movement, the state in accordancewith FIG. 27F is reached, where it can be seen that a clear kink 728 hasarisen in the wall of the head part 716 of the functional element 710directly adjacent to the plunger projection 756.

As the closing movement of the press continues further, the region ofthe wall of the head part 16 of the functional element 10 below the kinkposition 782 is now formed into an annular fold or to an annular bulge752. The face 754 of the outer plunger 742 now presses onto the top ofthe sheet metal part 730. The plunger projection 756 has now pressed thetop of the ring fold 752 flat so that its surface is arranged slightlybeneath the plane of the top of the sheet metal part 730 and isadditionally perpendicular to the longitudinal axis 724. The panel slug750 has now directly reached the end of the hollow space 718 of the headpart 16 of the functional element 10 and supports the ring fold 752 fromthe inside. The press is now completely closed in the state of thedrawing in accordance with FIG. 27G. The insertion of the functionalelement 710 into the sheet metal part 730 is now complete.

The sheet metal material and the material of the head part 16 of thefunctional element 10 is now deformed in the region of the grooves 739and noses 741 of the die 732 by the pinching of the annular fold by theplunger projection 756 so that the sheet metal material hooks up withthe material of the functional element here, whereby a high-qualitysecurity against rotation is created.

The press now starts to open, as shown in FIG. 27H. The tappets 768press the sheet metal part with the attached functional element awayfrom the lower tool 762 and lift the sheet metal part with the attachedfunctional element out of the die 732. The further opening movement ofthe press then leads to the shaft part 714 of the functional element 710being re moved from the plunger 742. The sheet metal part with thefunctional element attached thereto can now be removed from the pressand appears as shown in the representation in accordance with FIG. 27I.

It can be seen that the inner plunger 748 and the outer plunger 742 movein synchronism with one another during the total closing movement of thepress from the state of FIG. 27A to FIG. 27G and even also includingFIG. 27H. This can be achieved, for example, by the inner plunger 748having a head part of a larger diameter above the outer plunger 742,this head part coming into contact with the outer plunger 742 so that arelative movement of these two parts is prevented from this point on.The inner plunger 748 should, however, still be capable of upwardmovement relative to the outer plunger 742 to allow the insertion of thefunctional element 710 into the plunger passage of the inner plunger742.

FIG. 28 shows a possible plunger arrangement 842 in detail which can beused advantageously instead of the plunger arrangement 743 in accordancewith FIG. 27.

The outer plunger 842 is provided with an inner bore 886 which isarranged coaxially to the longitudinal axis 824 and displaceablyreceives the inner plunger 848. A supply passage 888 is shown on theright-hand size of the sectional drawing in accordance with FIG. 28Athrough which the functional elements 810 can be inserted from a feeddevice (not shown) into the plunger passage formed by the bore 886.Although the functional elements 810 shown in FIG. 28A approximatelyhave the shape of the functional elements 10 in accordance with FIG. 11,where the base of the transverse wall has a conical design, basicallyall functional elements described up to now can be used, above all thefunctional elements 710 in accordance with FIG. 25 or FIG. 27. It can beseen that the longitudinal axes 324 of the individual functionalelements are parallel to the longitudinal axis 824 of the plungerpassage 886 and that the individual functional elements are arranged inrows touching one another. However, due to the dimensions of the plungerpassage 886, only one functional element 810 at a time can be located inthe plunger passage 886.

When the press is opened, the outer plunger 842 is displaced downwardswith respect to the inner plunger 848, usually under the pressure of acorresponding spring until the end face 874 of the inner plunger 848,approximately reaches the level of the upper boundary of the supplypassage 888 so that a functional element 810 can be inserted into theplunger passage 886 by pressure in the direction of the arrow 890.

The outer plunger 843 in this embodiment is made in a plurality of partsand comprises a lower annular part 892 fastened to an upper part 894 byscrews (not shown). The lower part 892 has a central aperture 895 withan annular wall 896 of circular cylindrical shape which merges into aconical region 898. Both the circular cylindrical region 896 and theconical region 898 are arranged concentrically to the longitudinal axis824. The upper part 894 of the outer plunger 843 is provided with aconical recess 900 which merges into the plunger passage 886 via anannular shoulder 902. The conical region 900 and the annular shoulder902 are also arranged concentrically to the longitudinal axis 824 of theplunger arrangement.

In this embodiment, three segments 904, which are arranged at equalangular intervals around the central longitudinal axis 824, are locatedin the region between the upper part 894 and the lower part 892 of theplunger arrangement 842. The three segments 904, of which only two canbe seen in FIG. 16, together form a receiver 905 arranged coaxially tothe longitudinal axis 824 for a respective functional element 810. Thelower surfaces 908 of the segments 904 pointing radially inwards aremade as a segment of a thread cylinder which is designed to becomplementary to the thread cylinder 812 of the shaft part 814 of thefunctional elements 810. The upper surfaces 912 of the segments 904pointing radially inwards together form a passage 913 having a diameterwhich is somewhat smaller than the outer diameter of the head part 816of the respective functional elements 810. The radially outer surfaces914 of the segments 904 are designed as partially conical surfaces whichare complementary to the conical surface 900 of the corresponding recessof the upper part 894 of the outer plunger 842. The radially uppersurfaces 916 of the segments 904 are designed complementary to theannular shoulder 902 so that in the position of FIG. 28A, the partiallyconical surfaces 914 of the segments 904 and the partially circularsurfaces 916 fully contact the respective opposing surfaces of the outerplunger 843, i.e. the surface of the conical recess 900 and the annularshoulder 902.

In this position, the through passage 913 formed by the segments 904 ismade such that it is smaller in diameter than the outer diameter of thehead part 16 of the functional element 810. In this way, the respectivefunctional element 810 can initially not fall between the segments, butis rather supported at the upper end of the segments 904 as is shown inFIG. 28A.

The upper region of the respective segments 904 merges into a partiallycylindrical wall part 922 via a partially conical surface 920. Thepartially conical surfaces 920 of the segments 904 are opposite theconical surface 898 of the lower part 892 of the plunger arrangement 842in the position in accordance with FIG. 28A and are spaced therefrom.The partially cylindrical surfaces 922 of the segments 904 are oppositethe partially cylindrical surface 896 of the lower part of the plungerarrangement 843 and are radially spaced therefrom in each case.

To ensure that the segments 904 always return to the starting positionof FIG. 28A, tappets 928 biased by springs 926 are provided whose axes930 are inclined with respect to the longitudinal axis 824 of theplunger arrangement 843 and perpendicular to the conical surface 898 ofthe lower part 892 of the plunger arrangement 843. The spring biascauses the tappets 928 to be pressed against the partially conicalsurfaces 922 of the segments 904 contacting them directly such that whenthe press is open, these always assume the position shown in FIG. 28A.The spring bias is not very strong.

If the press is now closed, the inner plunger 848 is pressed downwardswith respect to the outer plunger and in this process presses therespective functional element 810 located in the plunger passage 886against the upper face of the segments 904. As a result of the slopedentrance to the passage 913 and the correspondingly inclined outersurface in the region of the lower face 820 of the respective functionalelement 810, the force exerted on the inner plunger 848 is sufficient topress the segments radially downwards in the axial direction 824 andradially outwards so that they press the pins 928 downwards until thepartially conical surfaces 920 come into contact with the conicalsurface 898 of the lower part 892 of the outer plunger 843.

The radially outwardly directed movement of the segments 904 causes theinner diameter of the passage 913 bounded by these segments to increaseso that the respective functional element located in the plunger passage886 is pressed into the passage between the segments 904 under the forceof the inner plunger 848. An intermediate stage of this movement isshown in FIG. 28B, and this movement subsequently continues until theupper shaft part 814 of the respective functional element 810 providedwith a male thread 812 is located in the lower region of the segments904, where these then move radially inwardly and upwardly under theforce of the springs 926 biasing the pins 928 until the thread segmentsin the radially inwardly directed lower surfaces of the segments 904engage in a form-locked manner with the thread cylinder 812 of thefunctional element 810. This situation is shown in FIG. 28C and it canbe seen that the front section of the inner plunger 848, which has asmaller outer diameter than the upper part of the inner plunger 848, isarranged in a form-locked manner inside the passage 913 formed by thesegments 904, which is of benefit for the centering. The functionalelement 810 in FIG. 28C has now reached a position which is comparableto that of FIG. 25A, and the piercing process to insert the element cannow begin and runs in accordance with FIG. 27.

Although not shown in FIG. 28, the arrangement is made such that theinner plunger 848 cannot move any further downwards than as shown inFIG. 28C. This can, for example, be prevented by the upper part of theinner plunger 848 being provided with a head which has come into contactwith the outer part 842 of the plunger in its lowest position inaccordance with FIG. 28C. The whole force of the press is nowtransferred via 30 the inner plunger 848 to the face 829 of thefunctional element 810 and via the outer plunger 842 and the segments904 to the thread 812 of the functional element. It is ensured in thisway that the thread cannot be damaged as it is received in a form-lockedmanner inside the complementary thread parts of segments 904 so that thethread cylinder cannot be compressed. If the shaft part 814 of thefunctional element is intended to be made hollow, the cylindricalprojection 930 of the inner plunger 848 can be designed accordingly andcan extend via an annular shoulder (not shown) pressing onto the end 829of the functional element 810 into the inner bore of the shaft part sothat the pressing forces can be transmitted to the functional element810 without any damage to this element by the pressing together of thewalls of the hollow shaft part needing to be feared, as this element issupported by the extended projection of the inner plunger.

It should be pointed out at this point that the number of segments 904is not limited to three. The minimum number required to realise thisembodiment is two; however, three, four or more such members can also beused, with preferably one respective pin 928 with bias spring 926 beingprovided for each member.

The lower ends of the segments 904 can, if required, be provided withnoses 956 which jointly form the plunger projection 756 of FIG. 27.

After the attachment of the functional element 810 in accordance withthe drawing sequence of FIG. 27, the press opens again, whereupon thesprung hold down member exerts a force on the sheet metal part with theattached functional element, with said force being sufficient to drawthe segments 904 downwards into the position of FIG. 28B in order torelease the shaft part 814. As the spring tension of the spring 928 issmall, the release of the functional element when the press is opened iscarried out without damaging the respective functional element 810 justattached.

After the release of the functional element 810 just attached, theopening of the press results in the outer plunger 842, which is biaseddownwards by the spring force, being pressed downwards, while the innerplunger 848 is drawn upwards until it reaches the starting positionwhere the lower end face of the inner plunger 848 has reached the levelof the upper boundary of the passage 888, whereby a new element isintroduced into the plunger passage 886 by the pressure in the directionof the arrow 890. The working cycle then begins afresh with a new sheetmetal part and with a new functional element 810, namely the functionalelement that is now located in the plunger passage 886.

The tool arrangement can be a station in progressive tooling where astrip of sheet metal is led through a plurality of stations to carry outa plurality of operations. The tool arrangement can, however, also beused in a piercing press which only performs a single working step forevery stroke. The attachment of the tool arrangement to a robot oranother kind of tool is also possible.

The functional elements in accordance with the present invention are notonly intended for use with purely metal sheet parts, but can also beused with a number of further components which can be understood ascomposite components.

Such components are frequently brittle or elastic components whichconsist of a material containing hollow spaces or pores and frequentlyof a material. The following materials can be given as examples ofmaterials used for the manufacture of components, in particular ofbrittle or compliant components, which can be fitted with functionalelements in accordance with the invention:

Metal Foams

These are highly porous metal materials whose pore size and distributioncan be set to a defined value in the manufacturing process and which areinteresting for a wide range of possible applications. Such metal foamsalso offer savings in material and weight, and thus also cost savings,for a variety of components. They can absorb impact energy throughprogressive deformation and can therefore, for example, be used forenergy-absorbing parts such as structural parts of vehicles which areintended to absorb impact energy to protect the occupants in cases ofaccident. Furthermore, they have excellent damping properties so thatthey can easily absorb or attenuate sound waves and mechanicalvibrations.

Metal foams made, amongst other things, of aluminum or magnesium andmetal foams made of steel are known. Different manufacturing processesare known which can be used for the production of such metal foams. Forexample, metal powder can be mixed with a chemical compound whichlater—in a thermal treatment—effects the foaming of the metal. Gas,which causes the foaming, is released at the metals melting point. Ithas already been possible in this way to produce foamed aluminum with agas portion of up to 97%. Steel foams can also be produced using thismethod. The process can be used for a wide range of elements and alloys.The possibility also exists of making metal structures from hollowballs, for example hollow steel balls.

For the production of magnesium foams with a gas portion of up to 60% itis known to embed thin-walled hollow ceramic balls in a magnesium matrixin a casting process, with magnesium alloys also being used and beingfreely selectable.

Such materials can be harder and more brittle or, however, softer andmore ductile than the starting alloy, depending on the matrix alloy.

After their manufacture, the foams frequently exhibit a cast skin whichis either removed or smoothed using a filler material. Foams with a castskin, which is optionally filled with a filler material, form a kind ofsandwich structure.

Sandwich Structures with Metal Foams

The metal foams described above can be produced with or without a castskin and with upper and/or lower covering layers made of sheet metal orplastic to produce material composites in the form of a sandwichstructure with a core made of a metal foam.

Properties such as scratch resistance, low or high friction, corrosionresistance and good wear properties can be achieved by the applicationof coatings or coating layers to the core. The corresponding componentsor any covering layers present can be coated using all known coatingmethods, i.e. using electroplated coatings, lacquer coatings or coatingsapplied, amongst other things, by means of PVD methods. When sheet metallayers are provided on a core consisting of foam, the sheet metal layerscan be glued or bonded to the metal foam core, with soldering or brazingmethods also being possible. Glues are normally used to achieve the bondto the core for covering layers made of plastic.

Another method to produce sandwich structures is to provide hollowsections made of metal or plastic, for example, in the form of sectionsextruded in an extrusion process, either completely or regionally with ametal foam core. This can be done by the insertion of elongate strips offoam metal, optionally with a surface bonding of the foam metal to thesection, or by the foaming of metal/foam mixtures in the hollow section.Open sections or shaped sheet metal parts can also be provided with aninsert made of foam metal (insert made of one layer of foam metal or ofa plurality of layers of foam metal) and then covered with a coveringstrip or section which is fastened to the open section in the marginalregion by welding, riveting, bonding or otherwise. Plastic foams orother materials in such composite structures can also be used instead offoam metal. A concrete use of such sections filled with foam metal or aplurality of fillers is the use as a B column of a motor vehicle whichcan be made by the filling of a pre-fabricated section, optionally witha subsequent shaping by bending or pressing.

The desired mechanical properties can be set by the section-wise fillingof such sections. For example, the desired rigidity or buckling strengthcan be achieved in one region and the desired deformation, for example,in the event of an accident, in another.

Other Sandwich Structures

Material composites consisting of a core with a honeycomb structure andof upper and/or lower covering layers can also be used, whereby thecovering layers can be made of sheet metal or plastic plates. The honeycomb structure can be made of metal, metal foils or of cardboard orpaper or of plastic or of cellulose or lingo-cellulose.

Materials with Brittle Fracture Characteristics

Such materials include castings made, for example, of magnesium,magnesium alloys and thermosetting plastics, with and without fillers.Such materials can also be used for components which are fitted withfunctional element arrangements in accordance with the invention.

Further Component Materials and Designs

Plastic components, components made of woods or pressed boards or thelike can also be used for the component assemblies in accordance withthe invention, with such materials usually having to be considered ascompliant as they normally yield a lot under the forces which prevail inthe making of a rivet joint.

Special material composites are also feasible which consist of acombination of one or more of the above materials, for example ofmulti-layer arrangements comprising a plurality of layers bonded to oneanother, whereby, for example, thicker components or components withmore complex shapes can be built up.

FIGS. 29 and 30 show two possibilities of how a functional element 1010in accordance with the invention can be used with a composite component1030.

FIG. 29 shows the functional element 1010 in the starting state in ahalf-section on the left-hand side of the central longitudinal axis1024, with the other half of the functional element 10 being madesymmetrically on the other side of the central longitudinal axis1024—with the exception of the thread, which naturally forms acontinuous thread cylinder with the shown half of the thread.

In deviation from the prior embodiments, a flange 1011 is provided herebetween the shaft part 1014 and the head part 1016 and, as shown here,preferably bears noses 1013 which serve as additional security againstrotation. The flange part 1011 with the features 1013 providing securityagainst rotation can, if desired, be omitted; but it does provide a morestable attachment of the functional element 1010 to the compositecomponent 1030 here. The composite component 1030 can have one of theembodiments given above for composite components.

Prior to the attachment of the functional element, the compositecomponent is prepared as is shown on the left-hand side of the centrallongitudinal axis 1024.

It can be seen that a cylindrical bore 1031 was made with a circularcylindrical wall in the component 1030 and that the upper layer 1033 ofthe composite component 1030 was formed into a swaged recess 1035. Thebore 1031 can be made by a drilling process or a piercing process, whilethe swage 1035 is normally made by a piercing step, for example in apiercing press. If both the bore 1031 and the swage 1035 are made bypiercing, this can be done in one step by means of a correspondinglyshaped piercing tool. The swage 1035 has a shape similar to that of theflange part 1011.

When the functional element is attached, which can be done using a diein accordance with FIG. 12, a form-locked joint is created between thehollow head part 1015 of the functional element 1010 and the lower layer1039 of the composite component 1030. This joint is very similar inshape to that of FIG. 15, in that the hollow head part 1016 is formed toa rivet flange 1037 in its end region and this rivet flange 1037 comesto rest below the lower layer 1039 of the composite component 1030 andin that the region of the hollow head part 1016 above this lower layer1039 is formed to an annular fold 1052. The annular fold 1052 forms aU-shaped annular groove together with the rivet flange 1037 in which themarginal region of the lower layer 1039 previously also defining thebore 1031 was received. It can, however, also be seen that the annularfold 1052 is not quite as strong as the annular flange 52 in the FIG. 15embodiment, which is understandable as it is not possible to subjectthis region to the stress of an outer plunger in this embodiment.Furthermore, this embodiment lacks a panel slug, as the compositecomponent 1030 was pre-drilled here. In other words, the lower end ofthe functional element 1010 in FIG. 29 is not thrust through the lowerlayer 1039 in a self-piercing manner. As no panel slug is formed here,it is not necessary to make the rounded annular depression or rollsurface of the die as deep as shown at 36 in FIG. 12.

As the composite component 1030 is supported on a die from below, and asthe functional element 1010 is pressed downwards by a plunger fromabove, the noses and features 1013 provided for security againstrotation are pressed into the upper side of the upper layer of thecomposite component 1030 in the region of the swage 1035. After theattachment of the functional element, the upper side 1041 of the flangepart 1011 is approximately flush with the upper side (in FIG. 29) of theupper layer 1033 of the composite component 1030. The core material ofthe composite component 1030 is deformed in accordance with theextension of the annular fold 1052 and the lower layer 1039 in theregion of the annular fold 1052 and the U-shaped annular groove 1053.

If no flange part 1011 is provided, a swage 1035 is unnecessary and theprepared component 1030 then has only a cylindrical bore, with thecircular aperture in the upper layer preferably having at leastsubstantially the same diameter as the outer diameter of the hollow headpart 1016.

FIG. 30 shows a slightly modified embodiment in comparison with FIG. 29.The component 1030 is here also prepared by the making of a cylindricalbore 1031, this bore 1031 however stops immediately above the lowerlayer 1039 of the composite material 1030. No swage 1035 is made in theupper layer 1033 of the composite component 1030 here, either. Thediameter of the bore 1031 corresponds—as also in the embodiment inaccordance with FIG. 29, at least substantially to the outer diameter ofthe hollow head part 1016 of the functional element 1010, which is hereidentical to the corresponding element 1010 of FIG. 29.

In this embodiment, the lower end of the functional element 1010 isequipped with piercing features which cause the stamping out of a panelslug 1050 in cooperation with a corresponding die (approximatelycorresponding to the die of FIG. 12), with this panel slug being pressedinto the hollow head part 1016 in the region of the transverse wall 1022of the hollow head part 1016 as a result of a central post of the diearranged at a higher position.

The form-locked joint in the region of the rivet flange 1037 is thenbasically formed identically to the embodiment in accordance with FIG.29; except that here, the annular fold 1052 is additionally supported onthe inner side by the panel slug 1050.

As no swage 1035 is provided in the upper layer 1033 of the compositecomponent 1030, the lower side of the flange part 1011 of the functionalelement contacts the upper side of the upper layer 1033. This is onlypressed in slightly, above all in the region of the nose features 1013pro viding security against rotation, to produce just the requiredsecurity against rotation. The composite component 1030 in both examplesis under a certain compression between the flange part 1011 and therivet flange 1037, which is of advantage for the quality and thestability of the joint.

The functional elements described here can, for example, be made of allmaterials which reach the strength class 5.6. Such metal materials areusually carbon steels with a carbon content of 0.15 to 0.55%.

In all embodiments, all materials can also be named as examples for thematerial of the functional elements which reach strength values of Class8 of the ISO standard as part of cold forming, for example a 35B2 alloyin accordance with DIN 1654. The fastening elements formed in this wayare suitable, among other things, for all commercial steel materials forsheet metal parts capable of being drawn as well as for aluminum ortheir alloys. Aluminum alloys, in particular such with a high strength,can also be used for the functional elements, e.g. AlMg₅.

The trials carried out up to now have shown that when the material 35B2is used, the ratio of the radial wall thickness of the head part to theouter diameter of the head part is in the region of between 0.15 and0.2. Higher values are to be desired as they increase the yield forcesand the pull-out forces. However, it must be ensured that the pressingin forces do not lead to an impermissible deformation. With a diameterof 8 mm, a radial thickness of 1.2 mm has proved to be favourable.

1. A one-piece functional male element formed as a single piece of metaladapted for use with a metal panel element of steel of drawing quality,and comprising: a solid shaft part with first and second ends; saidshaft part merging at said first end into a head part axially alignedwith said shaft part, said head part forming a hollow tubular walladapted for forming a rivet joint with a pre-pierced panel element underthe action of pressing forces applied to said shaft part; wherein theshaft part has a spherical formation with a ball diameter at said secondend, said shaft part having an at least substantially constant diameterover at least its total length from said spherical formation up to saidhead part and said ball diameter being larger than said shaft diameter;said male element being formed of a material which in the context ofcold deformation achieves at least the strength values of class 5.6 inaccordance with the ISO standard 898/1, dated August
 1999. 2. A rivetedone-piece functional male element formed as a single piece of metalconnected to a metal panel element of steel of drawing quality having athickness, an upper side remote from a lower side and a panel opening,the male element comprising: a solid shaft part with first and secondends; said shaft part merging at said first end into a head part axiallyaligned with said shaft part, said head part forming a hollow tubularwall adapted for forming a rivet joint with a pre-pierced panel elementunder the action of pressing forces applied to said shaft part; whereinthe shaft part has a spherical formation with a ball diameter at saidsecond end, said shaft part having an at least substantially constantdiameter over at least its total length from said spherical formation upto said head part and said ball diameter being larger than said shaftdiameter; said male element being formed of a material which in thecontext of cold deformation achieves at least the strength values ofclass 5.6 in accordance with the ISO standard 898/1, dated August 1999;wherein said metal panel element has a substantiallyperipherally-extending lip defining said opening at said lower side,wherein said head part is inserted through said opening; and whereinsaid hollow tubular wall is deformed to form a rivet bead ofsubstantially u-shaped cross section accommodating saidperipherally-extending lip at said lower side of said sheet metal panelby bridging said thickness of said metal panel element and to form anannular ring fold at said upper side adjacent said spherical formation.3. A riveted functional male element in accordance with claim 2, withsaid upper side of said metal panel element defining a plane, therebeing a recess in said plane, said recess merging into saidperipherally-extending lip, said annular ring fold being arranged insaid recess, wherein an upper side of said annular ring fold of saidhollow tubular wall of said riveted functional male element is arrangedsuch that it lies in substantially the same plane as said upper side ofsaid sheet metal panel.